1. Field of the Invention
The present invention relates to a wheeled work vehicle having a lower structure supported on the ground by front wheels and rear wheels, a swivel base mounted on the lower structure to be swivellable about a swivel shaft disposed between the front wheels and the rear wheels, an operator""s seat and an implement support unit which are mounted on the swivel base, and an implement supported to the implement support unit.
2. Description of the Related Art
A wheeled work vehicle of the above-noted type is known from Japanese Patent Application xe2x80x9cKokaixe2x80x9d No. 2001-97017. In this, a swivel base is mounted via a swivel shaft on a lower structure having front and rear wheels. On this swivel base, there are mounted an upper structure including a operator""s seat and a steering unit and a ground-work machine having a liftable implement. An engine of the vehicle is also mounted on this swivel base as a part or the upper structure, and the operator""s seat is disposed immediately above the swivel shaft. In operation, such wheeled work vehicle like this can travel on the road at a high speed with the front and rear wheels. The vehicle is capable also of effecting a ground work such as digging with swiveling the ground-work machine and also lifting up and down the implement supported thereto. However, since the engine is mounted on the swivel base, the upper structure has a significant rearward extension forming a very long distance between the swivel shaft and the rear end of the structure. Moreover, the rear end of the upper structure protrudes significantly from the rear end of the rear wheels. These result in not only running instability of the vehicle, but also great difficulty in a swiveling work in a limited space. Further, as the engine is mounted on the swivel base, the center of gravity of the vehicle is at a relatively high altitude, which adds to the traveling instability. And, because of the significant mass of the upper structure, the swiveling workability of the vehicle cannot be improved easily. In addition, the ground-work machine can effect only upward/downward pivotal movement. Hence, swiveling of the swivel base allows only a work forwardly of the operator""s seat, not allowing such sideways work as side ditch digging for excavating a wall edge to be effected by e.g. a backhoe. In this way, the application of this work vehicle is very limited and a digging or excavating work in a limited space is very difficult.
A wheeled work vehicle having an engine mounted on its lower structure is known from U.S. Pat. No. 2,893,502. In this, the swivel base including front and rear wheels supported thereto is disposed at a higher position than the lower structure. Hence, in the construction too, the center of gravity is high, resulting instability in the traveling of the vehicle as well as in a work effected by the implement.
A primary object of the present invention is to provide an improved wheeled work vehicle capable of stable work with lowered center of gravity, thus solving the above-described drawbacks of the conventional art.
For accomplishing the above-noted object, according to a wheeled work vehicle of the invention, the engine is mounted on the lower structure and the swivel base is disposed at a position lower than upper ends of the front wheels and rear wheels.
With this construction, the engine is mounted on the lower structure, thereby to reduce the mass of the upper structure and also the swivel base is disposed at a low position, so that the center of gravity of the vehicle is lowered for allowing stable traveling and working of the vehicle.
Further, in order to allow the engine to be mounted on the lower structure and also to improve the swivelability of the swivel base (e.g. for its 360 degree swiveling), the invention proposes another wheeled work vehicle. In this, the engine is mounted on the lower structure and the swivel base is disposed adjacent the engine. Further the operator""s seat mounted on the swivel base extends outwardly and upwardly from the periphery of the swivel base so as to be able to pass above the engine during a swiveling movement of the swivel base. According to a still further wheeled work vehicle proposed by the present invention, the engine is mounted on the lower structure and the swivel base is disposed adjacent the engine and lower than an upper end of the engine.
With the wheeled work vehicles of the invention having the above-described features, the swivel base including the operator""s seat and the implement is disposed at a position lower than the highest position of the lower structure so as to allow 360 degrees swiveling movement of the swivel base. And, by increasing the weight of the lower structure thus correspondingly reducing the weight of the upper structure, the traveling stability, the working stability, the swiveling workability are improved and also both vertical and fore-and-aft dimensions of the vehicle are reduced while ensuring easiness for the operator in getting on and off the vehicle as well as large space for the operator mounting on the vehicle and simplicity of the entire vehicle construction.
According to one preferred embodiment of the invention, the lower structure mounts, between the front and rear wheels, a fuel tank and a working fluid tank which are distributed on opposed sides in the traverse direction of the structure. This arrangement improves the lateral, the right/left balance of the lower structure.
According to another preferred embodiment of the invention, a power transmission mechanism for transmitting power of the engine to drive wheels is disposed forwardly of the engine and downwardly of the swivel base. Preferably, this power transmission mechanism includes a hydrostatic transmission (HST) having an input shaft and an output shaft which are disposed on the left and right of the transmission and extend substantially along the fore-and-aft direction. This arrangement allows the power transmission line of the lower structure to be disposed in this lower structure in a space-efficient manner.
According to a still further preferred embodiment of the invention, a rear portion of the swivel base is adjacent the engine and a forward portion of the swivel base is overlapped with the front wheels. This arrangement achieves maximum utilization of the space in the lower structure available for mounting the swivel base thereon and also greater fore-and-aft compactness of the lower structure.
According to a still further preferred embodiment of the invention, the implement support unit includes a support member and a swing shaft which are provided on the swivel base, and a swing member which can pivot about the swing shaft by a swing cylinder; and the swing member projects outward from a swiveling path of the swivel base. These arrangements allow stable support and lateral pivotal movement of the implement above the swivel base and prevent the swing member from adversely affecting the swivelability of the swivel base.
Further and other features and advantages of the invention will become apparent upon reading the following detailed description of the embodiments thereof with reference to the accompanying drawings.